ROHM's new breakthrough in power IC technology in the field of automotive semiconductors

Foreword

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Today, the world's major automakers are planning to develop and expand their HEV and EV investments in response to environmental concerns. However, since EVs are mainly powered by batteries and motors, at this stage, compared with fuel-powered vehicles, the driving distance is short, and there are still many problems in achieving popularization. Therefore, based on the high-efficiency and low-fuel diesel engine that has been popularized in Europe, the development of diesel hybrid power with a hybrid system added thereto is progressing.

In this case, automakers have raised the need for environmentally friendly, high value-added, and highly functional parts development. As always, with the development trend of these automakers, the multi-functionality of in-vehicle applications is growing, and the number of automotive electronic components is increasing year by year. In addition, even for low-cost cars and small cars in emerging countries, the increase in electronic components is inevitable for automotive development, and more and more products need to pay more attention to manufacturing costs and added value than ever before. .

This time, we will introduce the power supply necessary for the in-vehicle application to work in the on-board semiconductor. Power ICs can be divided into two categories: series power supplies and switching power supplies. ROHM's power supply development not only meets the above requirements, but also has been committed to the development of new technologies in each power supply development. Of course, the basic performance characteristics such as high-frequency operation and high-efficiency of the power supply IC are the first to bear the brunt. In addition, ROHM continues to promote the development of power ICs that meet the unique needs of the market. One of its great requirements is "lower current consumption." This is in the category of “added value” in market demand.

ROHM tailors new "power IC" technology for "vehicle semiconductors"

As the number of car accessories used increases, it is imperative to reduce the current consumption required for each accessory. In response to this situation, in order to achieve lower power consumption in in-vehicle applications, it is often possible to achieve low power consumption by maximally controlling the configuration required for constant operation. The "low power consumption of power IC" technology needs to meet the low power consumption of each component and the low power consumption requirement of the above-mentioned constant-time operating microcontroller power supply.

[Fig. 1] Example of action function when parking

The engine does not start. Only when the battery is powered on, the standby state of the car and the function of stopping (turning off), etc., are particularly important for low power consumption. When the engine is not started, there are air conditioners, electric windows, etc. Recently, with the development of electric power steering, the steering angle detection function when the engine is stopped is generally configured; when parking (blackout), there is a car navigation system, Security system, clock, etc. (Figure 1). The power of these functions is supplied by the main battery and the battery.

In addition, since the automobile is transported for a long period of time in the state of the entire vehicle, the amount of electricity accumulated in the battery is gradually consumed during transportation, and when the destination is reached, the battery may be exhausted. As a countermeasure, transportation is often carried out by removing the battery, but installation is required when reaching the destination, the process is increased, and the overall manufacturing cost is increased. Therefore, with the development of multi-functionality of automobiles, reducing battery power consumption has become a top priority. As a countermeasure against these problems, it is a very effective means to reduce the current consumption of the power supply IC (Fig. 2).

[Figure 2] Low current consumption of the car

The "BD7xxLx Series" developed by ROHM realizes the technological innovation of "circuit current 6μA"

In the series of power supplies, Roma began developing the world's top low current consumption LDO (Low Drop Out) - BD393x/394x series in 2005. This series of products has a circuit current of only 30μA and is excellent in performance. At the same time, it is also a highly reliable IC product for automotive ICs that can be used under severe conditions. Since then, Roma has continued to be at the forefront of the series of power supply low-power, and this time, the BD7xxLx series with lower current consumption has been developed. The current consumption of this series is only 1/3 of the current consumption required in automotive applications, and the circuit current is reduced to 1/5 compared with the previous IC, only 6μA (Figure 3). This is the world's top low current consumption LDO product in the field of automotive power ICs.

[Figure 3] The transition of the Rom circuit current

The BD7xxLx series not only has a small circuit current when the load current is "0", but also does not increase the circuit current of the IC itself when an output load passes. This is also trying to distinguish it from other power ICs. Although the increase in the circuit current depending on the load current is less than the load current, the power consumption of the circuit current may become a problem in the high temperature environment required by the vehicle, so ROHM is committed to achieving a completely low current consumption. However, there are several bottlenecks to achieve lower current consumption. In order to solve these bottlenecks, it is necessary to utilize the technology accumulated by Roma and its application (Fig. 4).

[Figure 4] Bottleneck of low standby current

In order to suppress the current consumption, a large resistor must be built in, which makes it impossible to further miniaturize the product, resulting in an increase in chip size and an increase in manufacturing cost. This is a huge obstacle to low cost. In addition, when a large resistor is built in, it may be susceptible to external noise.

In addition, even if it is not a large resistor, since the current value of the power supply IC using the low current consumption technique is small, it is more susceptible to external noise. Therefore, it is more important than ever to ensure that the noise immunity of the product is more than ever.

Second, there is also a problem of circuit responsiveness deterioration. Reducing the circuit current reduces the drive current and directly causes delays in circuit operation. Therefore, there is a concern that the output stability and the like at the time of the IC input fluctuation are deteriorated due to the delay of the circuit operation, and there is a concern that the delay start time at the time of IC startup is increased. The input terminal of the power IC is directly connected to the battery, and although the battery voltage is stable to some extent, it cannot be positioned as a stable power supply device. In particular, when the engine is started and the functions of the vehicle are working, the battery potential changes. Therefore, the stability of the output voltage when the input voltage fluctuates is an important characteristic.

Moreover, it is easy to be affected by leakage current under high temperature operation, which is also one of the problems. Although the leakage current is small, the built-in large resistance has a high possibility that the leakage current and the voltage generated by the built-in resistor cause a malfunction.

In response to these bottlenecks and concerns, ROHM's new product group BD7xxLx series has successfully developed the industry's top low current consumption and the same level as previous power ICs by introducing new circuits and optimizing layouts. The basic characteristics of the goods.

The lineup of this series of products has two output voltages of 3.3V and 5.0V, and has two output currents of 200mA and 500mA depending on the application. The package is a SMD package, and the SOP type package with a space-saving support substrate. From a small package to a package with excellent heat dissipation characteristics, it has a strong lineup for customers' use (Figure 5).

[Figure 5] BD7xxLx series product lineup

ROHM continues to develop switching power supplies with 20μA standby current

In the field of switching power supplies, ROHM is developing a series of products that achieve 20μA standby current. It not only realizes the high efficiency of the switching power supply in the past, but also achieves low current consumption and high efficiency at light load by SLLMTM (Simple Light Load Mode), which is helpful for the same LDO. Standby current design.

The low standby current of the switching power supply also has the same bottleneck as the LDO. However, the switching power supply has a problem that the LDO circuit has a complicated structure and many components, and the current consumption factor of the driving IC increases, and the switching operation is being performed, thereby reducing The power consumption of a switching circuit is often difficult. In addition, power loss can be suppressed by switching operation during overload, but it is difficult to maintain efficiency at light load.

This series of products automatically switches to SLLMTM during load hours. This SLLMTM extracts unwanted switching pulses, which are operated only by the necessary and minimum control circuits in the interval before the next switch starts, and other circuits stand by in the low current consumption state.

ROHM's automotive switching power supply, by introducing this SLLMTM, achieves low power consumption at light loads, and the power consumption at the time of overload is the same as that of the previous products.

Compared with the series power supply, the switching power supply is positioned as an effective countermeasure against problems such as heat generation and load current increase due to an increase in the number of components used. Compared with switching power supplies, series power supplies have advantages in terms of cost due to fewer external components and simple circuit structure. Series power supplies and switching power supplies are often used according to the situation, but in the future, switching power supplies should become the mainstream of low-power power supplies.

In summary, as the future development direction of ROHM, it will be the market demand for low-power design, not only reduce the circuit current, but also improve the power conversion efficiency (90% or more) and switching operation frequency (more than 2MHz) of the switching power supply. In order to achieve high responsiveness and miniaturization of accessories such as coil capacitors, we are constantly strengthening the development of the ROHM product lineup.

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